William F. Friedman and Elizebeth S. Friedman
- In full: William Frederick Friedman
- Born: September 24, 1891, Chisinau, Russia [now in Moldova]
- Died: November 2, 1969, Washington, D.C., U.S.
- In full: Elizebeth Smith Friedman
- Née: Elizebeth Smith
- Born: 1892, Huntington, Indiana, U.S.
- Died: October 31, 1980, Plainfield, New Jersey
William F. Friedman and Elizebeth S. Friedman were American cryptologists who helped decipher enemy codes from World War I to World War II.
William Friedman was still an infant when his family immigrated to the United States; he studied genetics at Cornell University (B.S., 1914). Elizebeth Smith majored in English at Hillsdale (Michigan) College (B.A., 1915). They met at the Riverbank Laboratories (Geneva, Illinois), where they both eventually became involved in cryptology, working often for the government in decoding diplomatic messages. In 1917–18 William served in the U.S. Army, partly in France, analyzing German code books.
After the war, in 1921, the Friedmans (they had married in May 1917) moved to Washington, D.C., where, over the years, Elizebeth Friedman worked for several government departments, notably cracking the codes used by rumrunners and other smugglers, and where William Friedman, in the War Department, became the chief cryptoanalyst in the Signal Intelligence Service, notably leading the teams that broke various Japanese codes, including ultimately the Purple machine cipher initiated by Japan in 1939. After World War II, William Friedman worked awhile for the National Security Agency, and Elizebeth Friedman for the International Monetary Fund.
William Friedman wrote The Index of Coincidence and Its Applications in Cryptography (1922), one of the standard works in the nomenclature and classification of ciphers. Together, the Friedmans wrote The Shakespearean Ciphers Examined (1957), in which they denied Francis Bacon’s purported authorship of the William Shakespeare plays and sonnets.